1. Field of the Invention
The present invention relates to an image forming apparatus having an electrophotographic image-forming process section, and more particularly, to improvements in a cleaning member in a corona discharger constituting the image-forming process section.
2. Description of the Related Art
An image forming apparatus having an electrophotographic image-forming process section is frequently used in a copier, a facsimile, a printer, a so-called multifunction machine having their features, and the like. A corona discharger is incorporated as one constituent member of such an image-forming process section. The corona discharger is used for a charging device for uniformly charging the surface of a photosensitive drum, a transfer device for transferring a toner image on the surface of the photosensitive drum to a recording medium (recording paper), and a discharging device for discharging from the surface of the photosensitive drum. Although a wire electrode has previously been used as an electrode of the corona discharger, the electrode presents a problem of generation of ozone. A stylus electrode which generates smaller amounts of ozone has come into extensive use.
Although the corona discharger using the stylus electrode is preferable as a charging device constituting an image-forming process section, such as that mentioned above, because of generation of small amounts of ozone, the stylus electrode is apt to attach extraneous matters (toner, paper dust, silicon, or the like) over time. When an increase arises in the amounts of attached matters, irregularities occur in electric discharge, which cause a failure in formation of an image in some cases. For this reason, as described in Japanese Patent Publication No. H07-43990, a corona discharger having a cleaning device which enables sweeping of a surface of the stylus electrode, as appropriate, has already been put into practical use. The cleaning device of the corona discharger disclosed in Japanese Patent Publication No. H07-43990 is configured in such a way that a stylus electrode is sandwiched between a pair of rotatably-supported rollers and that the pair of rollers can be slidably moved, while sandwiching the rollers, along a longitudinal direction of the stylus electrode.
Incidentally, in the cleaning device such as that described in Japanese Patent Publication No. H07-43990, both shaft sections supporting the pair of rollers are biased in a direction to face each other. Therefore, the rollers are rotated in the state that an urging load remains exerted on both surfaces of the stylus electrode. Accordingly, the load acts so as to impede rotation of both rollers, and sliding resistance also becomes great. In order to lighten such a load that impedes rotation of the rollers, support shafts must be arranged to support the rollers by way of a bearing member or a bearing member must be arranged to support a rotary shaft integrated with the rollers, to thus cause the bearing member to support the load. However, such a structure results in the necessity of providing a bearing member to both rollers, which leads to an increase in the number of components.
A conceivable way to prevent an increase in the number of components is to combine a shaft-rotational slidably-contacting member (a roller) with a non-rotational slidably-contacting member; to exert urging load only on the non-rotational slidably-contacting member; to insert a stylus electrode between the members; and to slide the members, thereby cleaning the stylus electrode. In this case, since the load is not exerted directly on the shaft-rotational slidably-contacting member, a bearing member for lessening the load that impedes rotation is obviated, and superior cleaning function is achieved without involvement of an increase in the number of components, and an enhanced practical value is expected to be attained. However, when both members are caused to perform nipping and when the members are slidably moved in the state that the stylus electrode is inserted in the nipped section, it may be the case where a stylus portion of the stylus electrode will catch a slidable-contact surface of the non-rotational slidably-contacting member, whereupon the stylus electrode is bent.